"On at least three occasions before 1998 other powers used the explicit or implicit threat of nuclear weapons to try and change India's behaviour," Menon said without elaborating.

Addressing the National Outreach Conference on Global Nuclear Disarmament, he said the global powers did not succeed in changing India's behaviour because of the "hard-headed leadership we were fortunate to have."

"Since we became a declared nuclear weapons state in 1998 we have not faced such threats," Menon told an audience comprising college students and a handful of diplomats.

He said nuclear weapons contributing to the country's security in an uncertain and anarchic world.

"There is no question that these weapons have done so, to the extent that they were expected to when we decided to become a nuclear weapon state," Menon said.

Observing that nuclear weapons make a contribution to the country's security in an uncertain and anarchic world, he said, "The possession of nuclear weapons has, empirically speaking, deterred others from attempting nuclear coercion or blackmail against India."

The NSA underlined that from the very beginning India has made it clear that its nuclear weapons were for deterrence and not "war-fighting weapons".

In an apparent reference to Pakistan, he said unlike certain other nuclear weapon states, India's weapons were not meant to redress a military imbalance, or to some perceived inferiority in conventional military terms, or to serve some tactical or operational military need on the battlefield.